In some aspects, message data is generated from a first representation of a message and a reference image. The message data is generated to hide the message such that generating a second representation of the message from the message data requires processing of a second image that is perceptually similar to the first image. In some examples, a degree to which the second representation of the message is perceptually similar to the first representation of the message is related to a degree to which the second image is perceptually similar to the first image.